The control of operating parameters of an incubator always has the purpose to determine the ambient conditions for a premature or newborn in the incubator interior so that the patient loses as little heat from its body to the ambient as possible. Maintaining the thermal metabolism necessary for the well-being of the patient means an increased effort by the patient which is intended to be reduced by the ambient conditions within the incubator. The following parameters are essential for maintaining the desired ambient conditions: incubator air temperature to prevent heat losses by convection, surface temperatures of the incubator hood or the cot to prevent temperature losses via heat conduction or heat radiation as well as the moisture content of the incubator air with this moisture content being most significant. Furthermore, it is important to supply adequate oxygen to the patient in order to support the metabolism generating the heat.
U.S. patent application Ser. No. 07/580,549, filed Sep. 11, 1990, is incorporated herein by reference and suggests coupling those parameters which define the required favorable incubator ambient, via a process computer in such a manner that input values for the parameters are inputted and stored which are orientated to selected variables particular to the patient. The selected variables are directed, for example, to body weight, age, and gestation age. Experience values for the corresponding incubator parameters are known which correspond to these selected variables. The input variables stored in this manner are compared to the actual values from the incubator and cause specific actual value combinations to lead to data as to the heat condition of the patient when there is a drop below pregiven tolerance values or when these tolerance values are exceeded. The desired value of suitable parameters is changed when the maintenance of a required heat condition is no longer ensured. The desired value for the incubator air temperature is increased when, for example, the comparison of the actual values to the stored input values leads to the result that the patient is hypothermic.
In this kind of control of operating parameters of an incubator in dependence upon measured actual values, it is, however, not considered that the change of one parameter also affects the action of another parameter on the thermal metabolism of the premature or newborn. Accordingly, the increase of the incubator air temperature means a reduction of the relative humidity in the incubator air for example, whereby the possibility of evaporation to the ambient from the patient's body is increased and therefore evaporation heat is removed from the patient. On the other hand, a reduction of the incubator air temperature means an increase of the relative humidity so that the body temperature of the patient can even be increased notwithstanding the low incubator air temperature because the capacity for giving up evaporation heat is reduced. Furthermore, it can be necessary that the needed supply of oxygen is reduced when there is a high incubator air temperature and a corresponding warming of the body core temperature.
If for this reason, one of the operating parameters must be reduced with respect to its desired value, then it is necessary to also adapt a second parameter to the changed conditions to obtain an optimal adjustment of the ambient conditions of the premature or newborn in the incubator. This would then mean the additional adjustment of an operating variable by the operator of an incubator which must then be continuously monitored by the operator. The care of the patient located in the incubator must, however, at all times be given priority. For this reason, monitoring of the adjustment of the operating parameters must be reduced to a minimum. This means that the operator is willing to adjust at most one operating parameter.